Use of the word 'stupid' to describe cultists is factually correct.
You can't just whip out a dictionary and think you're going to win an argument with it!
(Can you believe someone on another message board told me that once?)
Seriously, I see your point. Based on the definition, it is tecnincally accurate. I would ask then, is it a helpful description? For those who have gotten out, we see the light, we don't need to feel any worse for having made poor decisions in the past. We know it, without the need for some smart alec on a message board to taunt us with it.
For those still in, it will only alienate them from listening to useful information and feed their persecution complex.
I told a friend last night about being in a cult. He said anyone who would accept a cult is a moron. If someone tried to tell him about some guy who was raised from the dead, his response would be "Zombie!" I didn't get to talk to him more after that, but I would have pointed out how he may be cynical about religious or mystical claims, but how could he be sure he would discern the difference between a legitmate business and a commercial cult? Or a legitmate learning experience and an educational cult? Or a legitimate political action group and a political cult?
For all of these, singling out a particular group and warning against them is unhelpful. With thousands of cults of different kinds actively recruiting members, it's ridiculous to expect to learn about every one. And unnecessary. Learning about unethical recruiting methods would help immensely. There's no need for instructors to even focus on religious cults.